Brakes are an essential part of a motor vehicle. Brakes, whether they be disc brakes or drum brakes, often produce noise. The noise can vary in nature and has been called brake squeal, creep and groan, pinch-out squeal, and wire brush. This brake noise is undesirable because it interferes with the quiet ride of the motor vehicle. In addition, the operator may believe that the brakes are not operating in a proper manner because of the noise. The operator may thereby feel insecure about driving the vehicle.
Many efforts have been made to reduce the noise of brakes. The brake pads have often been made with quieter materials. In addition, efforts have been made to clean the drum or rotor from particulates which may produce noise. It is also known that slight lubrication of the rotating member can reduce noise without diminishing the braking effect of the brakes.
Lubricants have been incorporated in the brake pad itself. Graphite particles have been dispersed in the brake lining material up to a 10% concentration. Lubricating discs or rectangular shaped inserts have been embeded within the brake lining. Because the lubricating particles or inserts were embeded within the brake lining, the lubricant was often wiped off or otherwise dispersed from the lubricated rotor section before the lubricated rotor section engaged the leading edge of the brake pad. Effective lubrication of the rotor to reduce brake noise in this fashion would necessitate increasing the amount of lubricant concentration throughout the entire pad. On the other hand, diminished braking ability of the pads limits the increase of lubricant concentration.
It has been determined that most brake noise emanates from a leading portion or leading contact edge of the brake pad. It is, therefore, desirable to put lubricant on the rotating member in a fashion that would prevent the lubricant from being wiped off or otherwise dispersed before that lubricated section of the rotor engages the leading edge of the brake lining. It is desired to have the concentration of lubricant vary throughout the brake pad such that the leading edge of the brake lining engages the lubricant simultaneous with or immediately after the lubricant is applied to the rotor.